In recent years, demand for energy savings has increased, and thus, electronic devices such as power semiconductors and LEDs (Light Emitting Diodes) for purposes of reducing power consumption have progressively been popularized.
In such electronic devices, the number of devices mounted in the modules are reduced because of enhanced demands for miniaturization of casing sets, and ease of electric or optical design.
Thus, an amount of power assigned to each of the elements is increased.
As a result, a problem of enhanced heat generation from the elements arises.
Therefore, great importance has been attached to the provision of higher heat-radiation capabilities in order to secure reliability of the products.
Under such a background, wiring substrates with higher heat-radiation capabilities, in particular, high-heat-radiation substrates including metal bases, and resin wiring substrates combined therewith, have been developed (e.g., JP-A-2007-258590 and JP-A-2005-166868).
Such heat-radiation substrates including metal bases have a structure in which metal plates serving as heat-radiation parts, and the resin wiring substrates including electric wiring layers are adhered to each other.
In general, large-sized metal plates, and resin wiring substrates are adhered to each other, and the resulting materials are cut into separate pieces of desired sizes.
With regards to the method for cutting the materials into separate pieces, cutting techniques such as router machining, and shearing techniques using dies would generally be employed, as shown in JP-A-2007-258590.
However, when a large number of substrates need to be produced, and thus, high production capabilities are required, die-based shearing would be more effective in reducing costs.
In die-based shearing, burrs and warpages are formed on the surfaces of the metal bases.
When heat-radiation fins and the like are further placed on a heat-generation substrate equipped with electronic parts, through a heat-radiation grease, the grease thickness will be large due to the burrs and warpages.
As a result, the heat-radiation properties will be deteriorated.
For this reason, in cases where shearing is carried out, the punching direction is restricted to one direction, and thus, a direction in which burrs and warpages are formed is prevented from becoming a surface on which electronic parts are mounted, as shown in JP-A-2005-166868.